Osteoarthritis (OA) is a debilitating disease that affects human and veterinary, particularly canine patients. Because OA is not typically diagnosed early enough to prevent the clinical progression of disease, development of early OA biomarkers has profound ramifications for diagnostic screening, disease staging, treatment planning and monitoring. In dogs, certain proteins exhibit differential expression levels in synovial fluid when OA is experimentally induced. These are monocyte chemoattractant protein 1 (MCP1), interleukin 8 (IL8) and keratinocyte derived chemoattractant (KC), certain Apolipoproteins, and matrix metalloproteinases (MMPs). It is unknown however whether these or other proteins might be useful as potential biomarkers in spontaneously occurring OA in dogs or in other species including humans. Given the high potential value in being able to apply proteomics methods to diagnosis and prognosis of OA disease, and treatment monitoring and elucidation of OA disease mechanisms, it would be useful to identify new OA biomarkers and biomarker combinations with the ability to conveniently and reliably discriminate between individuals in which OA is present and those in which OA is not present, and determine the type and severity of disease burden.